# HL Math Paper 2- 24 Hours Later...

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1. Re: HL Math Paper 2- 24 Hours Later...
(Original post by Hyaline)
integral of 1/1+x^4 anyone............ I got some long thing with ln and arctan in it, most likely wrong........
This was another annoying thing. Substitution wouldn't work. I tried by parts and let dv/dx = 1 and u = 1/1+x^4. It was a long process....
2. Re: HL Math Paper 2- 24 Hours Later...
I substituted x= root(tan(u))........... it went horribly wrong xD. What did you do for the arrangements of girls and boys where there were 15 girls and 10 boys? Can you confirm 67.5cm for the string around the circles?
Last edited by Hyaline; 05-05-2012 at 13:29.
3. Re: HL Math Paper 2- 24 Hours Later...
(Original post by Hyaline)
I substituted x= root(tan(u))........... it went horribly wrong xD. What did you do for the arrangements of girls and boys where there were 15 girls and 10 boys?
I think a got the combinations of boys and the combinations of girls using nCr and then added together.... but my answer was really ridiculously high, which i wasnt confident about
4. Re: HL Math Paper 2- 24 Hours Later...
Hey guys, what do you think the grade boundaries for this year will be? by the looks of it i think it will be similar to last years, personally i felt the difficulty was similar to may 2011 tz2
5. Re: HL Math Paper 2- 24 Hours Later...
For part a) I did 15!*10!*2! for part b) I wasn't too sure I did something like 15C2*10C3
6. Re: HL Math Paper 2- 24 Hours Later...
(Original post by johndoe04)
The equation was something like, v^2 +dv/dt - 1 = 0. How did you go from there?
Ok, I attached an explanation for how to get the expression for v. Typo in my first answer- not arctan, just tan!

For the ball bouncing, it was the sum of the geometric sequence to infinity, times 2, plus the four meters it travels down before the first bounce- i.e. 156 meters in total.

For the integral of 1/(1+x^4), that was some bull**** to the max for 3 marks. I just used my calculators area function to trial and error my way to the a value- which I got to be 1.40, haha :P
7. Re: HL Math Paper 2- 24 Hours Later...
(Original post by Hyaline)
For part a) I did 15!*10!*2! for part b) I wasn't too sure I did something like 15C2*10C3
ok then i got that wrong i knda guessed....
that was like 6marks or 5marks rite? ****...

what do you think about the difficulty compared to last year's paper?
8. Re: HL Math Paper 2- 24 Hours Later...
(Original post by johndoe04)
This was another annoying thing. Substitution wouldn't work. I tried by parts and let dv/dx = 1 and u = 1/1+x^4. It was a long process....
9. Re: HL Math Paper 2- 24 Hours Later...
I put 160 -.- forgot about the 4 at the start, my marks are slowly dropping in my head.
10. Re: HL Math Paper 2- 24 Hours Later...
For the Poisson distribution question what did you guys get as m, I got 7 point something.
11. Re: HL Math Paper 2- 24 Hours Later...
holy f*ck!!!
12. Re: HL Math Paper 2- 24 Hours Later...
Not 15C2*10C3 sorry, I put 15C2*10C3*25C5.

67.5 for the string length ^^, I need confirmation .

Wow............ ****ing, IB wtf.
Last edited by Hyaline; 05-05-2012 at 13:51.
13. Re: HL Math Paper 2- 24 Hours Later...
(Original post by Hyaline)
Not 15C2*10C3 sorry, I put 15C2*10C3*25C5.

67.5 for the string length ^^, I need confirmation .

Wow............ ****ing, IB wtf.
YES i got 67.5 for string length too! was scared because most my friends forgot their answer...

hopefully i can get a 7, i estimate myself to get 90 plus or minus 5 marks for both papers
14. Re: HL Math Paper 2- 24 Hours Later...
(Original post by Hyaline)
I asked one of the maths teacher in my school after and she couldn't do it....................
and my teacher said might be a mistake in the paper
15. Re: HL Math Paper 2- 24 Hours Later...
(Original post by hin1994)
YES i got 67.5 for string length too! was scared because most my friends forgot their answer...

hopefully i can get a 7, i estimate myself to get 90 plus or minus 5 marks for both papers
**** !!! i got 71.23 for string length
damn im gonna so many marks.... i was hoping for a 6, hopefully i can still get the method marks
16. Re: HL Math Paper 2- 24 Hours Later...
(Original post by 526540828)
and my teacher said might be a mistake in the paper
Apparently, you can integrate it. Well, according to Wolfram Alpha.
17. Re: HL Math Paper 2- 24 Hours Later...
(Original post by johndoe04)
Apparently, you can integrate it. Well, according to Wolfram Alpha.
The person who wrote that question should be shot........... wtf, just wtf.
18. Re: HL Math Paper 2- 24 Hours Later...
(Original post by hkl1994215)
**** !!! i got 71.23 for string length
damn im gonna so many marks.... i was hoping for a 6, hopefully i can still get the method marks
how did you do the string calculation? i did it in a very unorthodox way..

i made theta the angle between the two lines at the centre, and got something like cos(theta)tan(theta)-(3/13)=0 then plotted it on my GDC. then i worked out the equation for total length of string and i substituted theta into that equation, giving 67.5m

edit: found out i was an idiot cause cos * tan = sin.. could have just used sin instead. luckily no marks lost for doing that
Last edited by hin1994; 05-05-2012 at 14:50.
19. Re: HL Math Paper 2- 24 Hours Later...
(Original post by hin1994)
how did you do the string calculation? i did it in a very unorthodox way..

i made theta the angle between the two lines at the centre, and got something like cos(theta)tan(theta)-(3/13)=0 then plotted it on my GDC. then i worked out the equation for total length of string and i substituted theta into that equation, giving 67.5m

edit: found out i was an idiot cause cos * tan = sin.. could have just used sin instead. luckily no marks lost for doing that
ok, then i got it wrong
i split the quadrilateral into two triangles and then used Pythagoras theorem etc.....
20. Re: HL Math Paper 2- 24 Hours Later...
Interesting method ^^, I used Pythagoras to get 4root10, and I used sin to get the angle 0.232 or something and the other one. Then I did 2pi-(2pi/2+2(0.232) to get one outer angle, same for the other side with the other angle. Then I found the 2 arc lengths. Then i just added it all up. Initially I drew an extra line to get a right angle triangle with hyp 13cm and one side of 3cm.

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